1. Field of the Invention
Aspects of the present invention relate to a can type secondary battery and a method of manufacturing a circuit board for the can type secondary battery, and more particularly, to a can type secondary battery including a circuit board that can prevent an explosion of the battery, and a method of manufacturing the circuit board.
2. Description of the Related Art
Recently, compact and lightweight portable electronic devices, such as a cellular phone, a portable computer and a camcorder, etc., have been actively developed and produced. The portable electronic devices include a built-in battery pack so as to be operable at places where a separate power supply is not provided. A rechargeable battery is used as the battery pack in consideration of cost. The typical secondary battery includes a nickel-cadmium (Ni—Cd) battery, a nickel-hydrogen (Ni-MH) battery, a lithium (Li) battery, and a lithium ion (Li-ion) secondary battery, etc.
The lithium ion secondary battery has an operating voltage that is three times more than the nickel-cadmium (Ni—Cd) battery or the nickel-hydrogen (Ni-MH) battery, which are usually used as a power supply for the portable electronic devices. In addition, the lithium ion secondary battery has been widely used because it has higher energy density per unit weight.
The lithium ion secondary battery is provided with a protection device to prevent the battery from exploding due to overheating or overcurrent. For example, a thermal breaker breaks a current at the time of overcurrent, or a safety vent opens when an internal pressure of the lithium ion battery is increased. Such protection devices prevent the lithium ion battery from overheating or exploding.
A safety vent and a circuit board may be used as the protection device in a can type secondary battery. When an internal pressure of the secondary battery is increased, the safety vent deforms so as to break a conduction pattern of the circuit board, thereby protecting the can type secondary battery.
However, the circuit board has a complicated structure and high production cost. Accordingly, the circuit board should be manufactured in consideration of a reliability that the circuit board is broken under a desired pressure, a type that the circuit board is installed in a can, production cost, and a manufacturing time. Particularly, the mass-produced circuit boards should be broken under a same pressure during testing so as to satisfy reliability requirements. In addition, the circuit board installed in the can type secondary battery should not be broken by an external impact during or after manufacturing, but should be sensitive enough to be broken by the safety vent. Further, the circuit board should be constructed so as to not occupy a large installation space in the can type secondary battery and so as to be easily installable. The circuit board should be changeable in design without increasing production cost if possible.